Electric switch



Jan. 13, 1931, H. P. CHANDLER 1,788,450

ELECTRIC SWITCH Filed Oct. 22, 1926 4 Sheets-Sheet 2 *IIIIVI Chrome 6mm x HOME/Q 7? CH/M/L EE Jan. 13, 1931.-' H p CHANDLER 1,788,450

ELECTRIC SWITCH Filed Oct. 22V, 1926 4 Sheets-Sheet I5 7 fr 43 z I Jan. 13, 1931. H. P. CHANDLER ELECTRIC SWITCH 4 sheets-Sheet 4v Filed Oct. 22. 1926 'Patented Jan. 13, 1931 UNITED STATES PATENT OFFICE Hoi/LEB. r. CHANDLER, or MANSFIELD. OHIO, Assreivoa To THE omo isi-mss COMPANY,

. .y or MANSFTELD, omo, A ,ConronApTroNfoE New JERSEY ELECTRIC SWITCH.

y lAppiicatidn inea octoberza, 192e. serial No. 143,509.

. My invention relates to electric switches and has Vparticular reference to `a vswitch adapted for use ink mines or other places n where gas ot an explosive character is present.

The object of my invention is to provide a device which is gas or flame proof and by kwhich the electric circuits canbe made or brokenv without danger of igniting the gases.

Another object. oi' my invention is to provide a device in which contacts can be made and broken in connection'with the device, but outside thereof. and whereby sparking or arcing is prevented andv this is brought 15 about by arranging the contacts to and Afrom the device so that they may-be made or broken only when the switch isin its open position.

Another object of my invention is to pro# vide a device in which the cover cannot be 2.0 removed or replaced with theV switching mechanism in a closed or partially closed relation to the terminals or a device in Vwhich the switch is inoperative until the cover has been entirelyl replaced. a5 A further object of my invention is to provide a quick break action to the switch in breaking the Circuits.

Another object ot my invention is to prol vide a switch in which there is a plurality of 3v breaks so that the a-rcing'upon opening'a cir'- cuit is divided between two or more breaks..

Another object of my invention is toprovide a switch of the'quick break rotatable type in which the rotating portion and its 33 mechanism is'removable with the cover of the device.

Another object of my invention is to provide a switch in which the circuit or circuits cont-rolled by the switch. are protected by fuses within the switch.

A further object is to arrange the device so Y that the Jfuses cannot be inserted or removed while the switch is closed or the termin als to i5 which the fusesl are attached arealive.

Another object of my invention is to provide means for locking the cover and casing against separation by unauthorized persons.

A still further object of myinvention is to 5e provide means to relieve the strain upon the detachable *cables whichv make temporary connection with the device.

Other: objects will be apparent to those skilled in the. art as I proceed with the` defl scription of my invention.

My inventionresides in the ne w and novel construction, combination and relation of the various parts herein` described and shown in the accompanying drawings.`

Inthedrawings'. Fig. l is a top view of my rinvention showing` the exterior View of the switch when in a closed position with auxiliary cables secured thereto and which lead tothe apparatus controlled bythe switch. Y' 'Y Fig. Q'is a side-'view of Fig. l.

Fig. 3 is a sectional view of my switch on the line 3 3, of Fig. l. i v

Fig. 4 isa sectional view of my switchen the line 1T-*4 of' Fig. 1. i

Fig. 5 is .av sectional'fview on the line 5,-5 of Fig. 1.

Fig. member taken on the line 6-6 of'. Fig. 5.

Fig. 7 is a sectional view onthe line 7 7 of Figs. Sand 5. f

Y Fig. 8 is a. sectional view on the line 8-8 of Figs. Band 5.

Fig. 9 is a developed view of the' inner circular insulated lining of the casing to show portant `features of myk invention taken on the line 11-11`0 Fig. 4l and Fig. 9.

Fig. 12 isanend View ofFig. 9.

In the preferred embodiment ofpmy invention I employ a casingv 1, preferably made of metal, and threadably secured thereto is a cover 2. The threads are of suilicient'length and fit suliiciently Vclose so that under normalA conditions gas cannot enter the casing and any flame or arc produced within the casing canl have no effect upon the exterior gases.

61 isa sectional view of therotatab-le There are four openings shown in the upright side of the casing although the number of such openings may be varied to meet the requirements. In the present case the four openings are .intended to take care of the two sides of a circuit. In the bottom of the casing is a disc of insulating material 3 which is not only an electrical insulator'7 but is non-inflammable and also water proof, such as fiber, asbestos inuregnated with a water proofing compound or bakelite composition.

Snugly engaging the interior side wall of the easing is aninsulating member 4 which can be made in one or more pieces and is shown in a -developed view in F ig. 9. This insulating member 4 has four openings in the side to correspond and registerl with the four openings through the side wall of the casing previously mentioned.

Passing through the openings in the side wall of thecasing and insulating member 4 are terminal members 5 each surrounded by an insulating bushing 6 which electrically separates the terminal from the metallic casr ing 1. The bushings G members 5 are provided ders and the bushings G are each provided with a shoulder engaging the casing 1, While the inner end ofthe terminal member 5 ,is provided with a thread engaged by the combined nut 7 and spring clips 8 (see Fig. 9), which when drawn up tight draws the shoulders on the parts referred to into close engagement with each other and securely locks the terminals 5 and the bushings 6 in'position, and with properly fitting parts and the use of cement or gaskets, if necessary, the side openings through the wall of the casing are rendered gas tight. The construction of the bushings and terminals just referred to also locks the insulating member 4 in position with respect to the casing.

The terminal members are positioned ninety degrees apart and each terminal is provided with a socket and two of the adjacent terminals are provided with cables 9 and 10 respectively and which are secured. permanently, one in each soclret, and these cables are, as a rule, connected permanently to the source of power.

The casing is provided with four lugs 11 for mountingl the switch .in permanent position. One of the lugs is provided with a pair of chains 12 to the free end of which is connected a snap hook 13 adapted to snap on and olf the cable clamps 14 when desired.

The cover and casing are provided wi h lugs 15 which have registering holes when the cover is in its final closed position and a padlock 1G can be inserted through the registering holes and the casing loclized against opening by an unauthorized person if desired.

The terminals opposite those to which the cables 9 and 10 are permanently secured are and the terminal 1th, engaging shoularranged to have connected thereto a plug connection 17 and which connection can be applied to or removed. from the terminal under proper conditions. Each plug connection 17 has an inner terminal. 18 provided with a socket at one end to receive the cable 19 or 2O in fixed relation. The terminal 18 is surrounded by the insulating sleeve 21 which is threadably secured to the terminal andthe insulating collar 22, which in turn is secured to the sleeve 21. The sleeve 21 can extend away .from the busl 22 any distance desired, although six or eight inches is sufficient in order @te provide a grip for the hand in applying or removing the plug contact. The parts. 21 and 22 can, if desired, be made of one piece as hy molding or utting from solid material.

lt will be noted that when the plug contact 17 is in position that there are no exposed parts of the live members and when the plug contact 17 is removed the terminals 5 are well protected from contact therewith. The insulating bushing 6 can be molded on to the terminal 5. if de, fred, which is common practise in this class of work.

The interior surface ofthe cover 2 provi red with an insulated lining similar to that of 8.

The cover 2 is provided with an upwardlyY projecting 24 having a passage theret 'ough and in which is mounted a shaft 25 having 'the cellar 2G at the inner end and provided with the oppositely projecting arms 27. Mounted upon the shaft 2.3 is a collar 2S from which project the arms 29 at right angles to each other with an intervening luaee 30. The cellar 28 is secured to the shaft 25 by means of the fet screws 3l and provides a means of maintaining the collar 26 in close Contact with 4A.he inner face of the cover 2.

Also mounted upon the snait't is another collar 32 which is provided with a boss 323 which is threadably secured to the handle 3J.. The collar 32 has a limited amount of rotation relative to the shaft 25. The upper end of the shaft 25 provided with the upwardly extending and spaced lugs as shown in Fig. 8, while the upper end. ofthe collar il?. to which the handle attached is provided w ith the oppositely disposed and inwardly project' ig lugs 36 adapted to en e and cooperate wit the lugs and permit ff an amount of relative rotation equal to the space 37 as shown in Fig. 8.

lt will be evident that when the collar 32 is rotated by means of the handle 34 the lugs 3G are arranged to engage with the lugs 35 on the shaft 25 and force movement of the shaft 25. The shaft 25 is hollow throughout its length and extending uijiwardly within the shaft 25 from the lower end is a Stud 3S provided at its uy Eer end with a slot to receive the end 39 of the spring 40. 'l'his arrangement anchors the lower end of the spring 40 to the shaft 25 and prevents lUfll n ly securedito the collar 321:0 which the handle 34 is attached, and that there isa permitted' relative movement ofthe handle witlirespectA relative movement of thek l lower end ofVV the spring and the shaft Q5. Extending .imvardlyy from the'u-pper end: of the sbalt al plug 11. having ak flange 42 at its upper und and a slot infits lower endIto-receive the upper end 43 of the springe() and thereby to the shaft 25, and by properly tensioning the springllOfby adjustment of the plug 41'there will be a normal tendency of the handle and shaft to rotate relative to each other through thel action of the spring thereby giving to the shaft a quick movement through the tension of the spring when the handle is moved in a direction 'tending to open the switch, andl ai preliminary movement of: thek handle in a direction toyopen the switch will tend to increasey the tension in the spring' 40 and theengagement of the lugs'i-f withV the higsVl will force the switch from its closedV position and as soonv as released the spring tensionv willthrow the switch quickly out of j engagement with its contacts thus providing a. quickbreak switch;

To the upper end of the plug' 41 is secured a cap 45 by meansof the bolts 46 which` en- ;.gagc with the lugs 35 as shown in 8,

and pass through slots 47" providedin the flange '42 andV abovethe lugs' 35; The purpose of theI cap is to seal the adjustment of the spring tensiony and against easy Vtarnpcrni'g therewitlr,and the loosening of' the Y screws 16canlieprevented byv drillinga small hole through ythe head of eachf and passing a small wire 48 therethrough 'andv twisting" and.' soldering the same in: fixed position.`

To the lower face of the,arms27`is: secured a circular discv of insulatingmaterial 49 and*r twospaced insulatingmembers 50 by means vofthe screws 51"'. To the lower face ot the insulating plugs 50 is secured the insulated disc 51 bymeans of the screws 52 seeFig. 61)'.

ll'flbunted: upon the upper faceoflthe disc 5212 at diametrically oppositepointsare the terminal members 53, the througl-i bolts 54e securing theterminals 53 in position, and each terminal 53 is provided with a blade 55- to engage with the spring contactsS, shown in Fig. 3, when the switch is in closed position'. Connecting the terminals 53' is an enclosed fuse From this it will be `seen thatv when the switch is closed, as shown in Fig. 3, the oppositelyl disposed terminals 5- will be elec trically connected. 4

Mounted upon the underside of the insulating disc 51 and rotated ninetydegrees from the fusible connection onthe upper sidel of the disc 51 is a fusible element Dl which has terminals 56 similar totheterminals-SB and provided with the blades 57 which en-V gage with the springy clips 8-sh`own in Fig; 4,

and connect the terminals 5, shown in Fig. 4,

when the switch is in a closed position.

- From this description it will be vseen that when the switch is closed thev diametrically opposite terminals projecting through the casing arel electrically connected byfmeans of` a, fused connection, and from theprevious description it will be seen that the switch is; closed when the handle 34 is'rotated in"` one direction, as for'instance, in a vclockwise'di'` rection', and the switchlis opened by af quick break movement when the handleis moved in j Y an anti-clockwise direct-ion;

v The discs 58 are of insulating lmaterial and are for the purpose' of covering theV screw heads used in securing' the terminals'@ andv 56 to the disc 51 thereby addingextraprotectionagainst leakage and short circuits withy Ain the switch. y j Y The insulating memberll is arranged with a v vertical and horizontal slots by means ofAl whichA the opening and* 'closing of lthe casing is ycontrolled so that thev same cannot take place onlywhen thev switch mechanism is in closed position with respectatothe terminals, v. and this is brought about by the cooperation- ,of the vertical and horizontal Vslots withV the switchy blades 5.5 and '57 and alsothefmember i 51 with the terminal parts 7-8;

In Fig. 9- is shown the inner face of the insulating member 4 in't a developed form as thoughthe insulating member was removed from its casing and splitr along 'the lower edge orline X (Fig. 1.0)v andl unrolled the, direction of" the arrows A and B.

The various terminals projecting through. the'casing are also sliownin position in Fig. 9 withv relation to theyslots. When the switch isv in a vclosedl position the terminals-shown on the lines Y'andf Y are connected as by the fused connection@ and the terminals shown on the lines X and X will be connected by the fused connection D. While in thisposition it will be apparent that the cover cannot be unscrewed because lthe rotatable approximately degrees, which will mean that in the open position the, connection C would' coincide with the lines Ya and Y", and

in this position the cover can be unscrewed andtheswitching mechanism can be removed throught the vertical slots shown in the de,-

veloped Figf9 and corresponding with the lines X", Xb, Y" and Y). l Then the switch is in the fully opened positiony as just de4 scribed, the cover can be rotated and as the cover rotates it will naturally rise and move along the axis olf rotation and with it the rotatable switching mechanism, and the blades being positioned in the slots referred to, there is no obstruction to their rif-ring with the cover and when the cover has been fully rotated outfof thrcadable migagement with the casing the cover and rotatable switching mechanism is removed as a single unit, leaving the interior of the casing,lv substantially free of all part-s, excepting the insulating member 4; and the vthrough termina-ls.

f Should an attempt be made to remove the cover while the switch isin a partially open position7 it will be found that it is impossible to do so for the reason that the blades 55 will be in engagement with the upper horizontal slots coinciding withthe line lO-1O of Fig. 9 in the 'insulating member Ll, and the blades 57 will be in engagement with the lower horizontal slots coinciding with the line 11--11 lof Fig. 9, or it will be found that the disc 51,

which positioned below the upper spring clips 8, will engage with the upper spring' clipsv 8 and prevent the rotatable switch mechanism and cover from being` moved npwardly.

ln regard to the engagement of the disc 51 with the spring clips 8, it will be noted in Fig. 3 that the diameter of the member 51 is such that it will just pass through the circular opening formed by the ange 59 in the insulating member 4, and in order to bring it to its position below the upper spring clips 8, it is necessary to removetwo opposite sides of the disc 51, as shown in Fig. 6. The short diameter of the member 51 is slightly less than the distance between the inner ends of the upper spring clips 8 and when the rotatable switch mechanism is in proper position to be removed the member 51 is in such position that its short diameter is positioned liel'ween the inner ends ot the upper spring clips 8. In other positions of the rotatable switch mechanism the upper spring` clips 8 will overhang the member 51, as shown in Fie. 3.

,Tn replacing the rotatable switch member it is possible to startthe insertion et the blades 57 in the slots corresponding to the lines X and X. but as this is an improper assembly condition. the disc 51 will come in Contact and rest upon the upper projecting` spring clips 8 and prevent the insertion oit the rotatable member within the casing.

I also provide means for preventing the closing of the switch until the cover has been entirely replaced to its linal position or within a halt or one turn thereof, and this is brought about by the tact that the lower blades 57, which enter the vertical slots indicated as Xa and Xb in Fig. 9, cannot rotate or be rotated untilthe blades 57 have moved downwardly through the screwing on of the cover until they coincide with the horizontal 50 and the clearance between the thickness of the swi. l; blade 5"? and the width ot the slot GO is very small; lt au attempt is made to rotate the switch mechanism while the blades 57 are in the vertical slots corresponding e o X and Xb, they will merely en- Yage the shoulders 61 until they coincide with the slots 60.

il t the lower end ot' the vertical slots coin* ciding with the lines X and Xb are rubber bumpers 652 which are composed of soft yielding rub Jer and have their upper faces slightly inclined and tend to act as a cushioning in operatingthe switch from a closed position to an open position, and prevent the switch blades 57 trom striking the side 63 ot the slots Xa and Xb with any great appreciable torce.

The arms 29 are bent downwardly at right angles and their lower ends are adapted to coincide with the two adjacent terminals through the side of the casing which are ada/.Lted to receive the removable plug contacts, and when the switch is in the closed position, it the plug contacts have not been properly positioned with respect to the terminals, then it will be impossible to connect plug contacts with the terminals as the lower end ot the arms 29 will .interfere and pre.- vent such connection, and also if the plug contacts have been positioned with respect to the terminals and the switch is in a closed position, then the arms will be engaged by the flange 64 on the plug contacts and prevent the withdrawal of the plug contacts while the switch is closed.

Assuming that the switch has been properly installed and the connections 9 and 10 made to the source of power, then if it is desired to connect the leads 19 and 2O from some machine to be operated to the switch, it is only necessary to move the switch handle until the arms 29 are out of alinement with the contact terminals through the side of the switch and which insures the opening of the switch and permits the connection of the plug contacts with the side terminals and this having been done, the switch handle is then rotated in a clockwise direction which eventually closes the switch and connects the cables 19 and 20 to the cables 9 and 10 respectively.

To remove the connection between the cables 19and 2O and the switch device, it is absolutely necessary to move the switch handle in an anti-clockwise direction, which first increases thetension on the spring ll0 and then brings the lugs 35 into engagement with the lugs 36, and which in turn forces the movement ot' the rotating switch mechanism until the blades 55 and 57 disizo engage with the spring clips 8 at which time Y nection lbetween thecables 19 and 20 andl theswitch, I secure yto `each cable adjacent the plug contact the clamp 14 providedwith means, such as an eye to which the snap hook 13 secured to the chain 12 can be attached thereby relieving the.` strain between the plug contact and the terminal of the switch. y v v If, for any reason, it is desired to examine the inside of VtheV switch, it `is then necessary to movejthe .switchftozits fully open position in which the blades andf57 correspond with the vertical slots Ya, Y?, Xa and Xb, then to unlock-andremove the padlock, if in position, and thentofrotatethe cover thereby moving the cover axially hof the switch and with it the switching mechanism, `and as soon as the cover has been rotated approximately a half to one turn it will be `impossible to rotate the switch to a closed position thereby insuring the switch to remain open -until after the cover has y been removed. l Y

When it is desired to re-assemble and close the switch, it is then necessary to position the blades 55 and 57 in proper relation with the vertical slots Y, Y", Xa and Xb and-then to rotate the cover` thereby moving it'axially toward the casing, and it will be found impossible to rotate the switch mechanism until the cover has reached its final position vwithin approximately one-hall to one.turn, thus insuring the casing being safely closed before it is possible to close the switch and possibly causing an arcing, `which might be very disastrous were the switchused in a gaseous mine. Having the fuses enclosed within the gas tight casingis also ya decided advantage in a gaseous mine as it protects the circuits ,and also avoids the iashing'of the rfuse igniting the gases, and combines in one device all the safety features required in a device-of this character by the Bureau of Mines. Y v l It is sometimes desirable to ground the casing and for that reason I provide the casing with a lug having ank opening to `receive a cable66, which is securedzto the lug 65 by means of the screw 67. The cable 66 can be attached to a ground at some convenient point thereby grounding the casing.

There .will be. modifications which will suggest themselves to those skilled in the art, but viwal; ajb@ limited only bymy claims. v y

YI claim: f

g 1. A switch comprising in combination a casing and al removable cover, concealed means .interlocked by rotation oi one of the said' parts relative to the other about a common axis to secure the parts together, insulated terminals passing through a wall of the casing, `contact plugs to connect to the ter-` minals,` a vswitch mechanism to connect `and disconnect theterminals, a swinging locking member to engage the plugs and prevent the disengagement of the -plugs when the switch is closed and means operated simultaneously with the closing of the switch mechanism `to prevent 4the removal of the cover while the switch is closed.

2. A switch comprising a` casing and a re,- movable cover secured together, insulated terminals passing throughthe casing, contact plugsto connect to the terminals, a' switch mechanism to connect and disconnect the terminals, a locking member arranged to operate simultaneously with the switch mechanism and to lock the plugs against removal when the switch is closed, and means on the casing to be engaged by means on the switch mechanism and concealed means on the cover to engage concealed means on thecasing to prevent the removal of the cover while the switch is closed.

3. Av switch comprising a casing and a removable cover secured together, insulated andixed terminals passing through the side walls of the casing, contact plugs to connect to `the-terminals, a switch mechanism provided with a blade secured to and removable with the cover vrelative to the tiXed terminals and adapted to connect the terminals, means on the casing to be engaged by the switch blade to prevent removal of the cover while the switch is closed and vmeans to prevent the removal of the plugs while'the switch is closed.

4. A switch comprising a casing and a removable cover and securing means interlo'cked by rotation or" one ont the said parts relative to the other part, to secure the parts together, insulated terminals passing through the casing, contact plugs to connect other terminals, a switch mechanism secured to and removable `with the cover to connect the terminals, means to prevent the removal of the plugs while the` switch is closed, and means on the switch interlocked with means onthe casing to prevent disengagement of the securing means to prevent removing the cover while the switch is closed.

5. A switch comprisinga casing and a removable cover securedtogether by a screw threaded connection therebetween, insulated terminals secured to the casing, contact plugs -to be connectedto and disconnected fromthe terminals, a switch mechanism secured to and removable with the cover t0 connect the las* terminals and means` to prevent the connecting et the plugs or removal of the cover lwhile the switch is closed or replacement 01"' the cover while the switch is in a position to connect the terminals. i y

6. A switch comprising a casing and a removable cover secured together, insulated terminals mounted externally and internally ot the casing, plugs arranged to be either connected to or disconnected trom the terminals, a switch mechanism secured to and removable with the cover to either connect or disconnect the terminals, means to prevent either the connecting or disconnecting ot the plugs while the switch is closed and insulated means on the casing to interlock with means on the switch mechanism to prevent either the removal or replacing ot the cover while the switch mechanism is in a closed position relative to the terminal members.

7. A switch comprising a casing and a removablecover, the cover and casing secured together by a concealed interlock between the cover and casing and operated by relative rotation ot the cover and casing in either direction depending upon the cover being removed or replaced, insulated terminals passing through the casing and arranged for connections thereto exterior ci the casing, a switch mechanism secured to and removable with the cover, means exterior of the casing to operate the switch mechanism to its closed position and means interposed between the switch and exterior operating means biased to open the switch with a quick break and means to prevent either the removal or the replacement ot the cover when the switch is in its closed position relative to the terminals.

8. A switch comprising a casing and a cover attachable and removable by rotation and means interlocking the two together to form a gas tight compartment, insulated terminals secured to the casing and having means to connect thereto exterior of the casing, a rotatable switch mechanism secured to the cover and removable with the cover, means secured to the cover to operate the switch mechanism to its open or closed position and means to impart to the switch mechanism a quick motion when the switch mechanism is moved from its closed position.

9.,A gas and flame proof switch compri-sing a casing, a rotatable removable cover interlocking gas proof connection between the cover and casing, a switch within the casing and operable by a means from without the casing, an insulated terminal having a gas proof connection to the casing, a plug adapted to be connected to the terminal, means operable by the iirst said means to hold the plug in engagement with the terminal while the switch is in closed position and means to prevent the removal of either the plug or the cover while the switch is in closed rela# tion to the terminal. Y f

10. A switch comprising a casing, a cover for the casing secured thereto by a. screwthreaded connection between the cover and casing, a switch mechanism within the casing and means secured to the interior side wall of the casing cooperating with the switch mechanism to prevent removal of the cover while the switch is in closed relation to circuits connected thereto.

11. A switch comprising a casing, a removable cover, a switch mechanism within the casing and secured to and removable with the cover and rotatable therewith, a handle to move the switch mechanism to either its open or closed position and a spring connecting the handle and switch mechanism to transmit a yielding motion to the switch to cause a quick break opening of the switch and means to prevent removing the cover until the switch mechanism is in its fully open position and auxiliary concealed means on the cover and casing cooperating to prevent removal ot the cover unt-il the switch is open.

12. A switch comprising a casing, a removable cover interlocked by rotation with the casing, a switch mechanism within the casing and secured to and removable and replaceable with the cover, a rotatable shaft secured to the cover only to move the switch mechanism to either its open or closed position, the casing and cover forming a gas tight receptacle and the cover removable only by rotation about the axis of the shaft and means to prevent replacing` the switch mechanism within the casing only with the switch mechanism in its fully open relation.

13. A switch comprising a casing and a removable cover screw-threaded to the casing, a switch mechanism within the easing and means on the casing,r cooperating with the switch mechanism to limit the rotation of the cover until the switch mechanism is in its open position.

14. A gas and llame proof switch comprising a casing, a removable cover secured thereto, a rotatable switch mechanism within the casing, means around the inner periphery of the casing to engage with the switch mechanism between the closed and fully open position of the switch to prevent removing the cover until the switch is fully open, temporary connections to the switch mechanism and means external of the casing to prevent making or removing the connections while the switch is closed.

15. A switch comprising a casing and a detachable cover secured thereto by interengaging means operated by relative rotation of the cover and casing, terminals secured to the casing to receive conductors exterior of the casing and forming an airtight connection therewith, a switch mechanism within the casing to connect certainot the terminals,

- terminals.

the switch comprising a plurality of connecting devices mounted on a rotatable insulated member and positioned in different `parallel planes with their axes at right angles, means to secure the rotatable member to the cover, means to operate the rotatable member from without the casing and members of the switch l' vto the inner surface of the casingprovided with circumferential slots and slots transverse to said circumferential slots and the said slot-s coacting with the switch mechanism to prevent removal of the cover until the switch is fully open and preventing closf ing the switch until the cover is substantially replaced.

17. A switch mechanism comprising a casing and acover removably secured together, two pair of terminals extending through the wall of the casing and each Ypair positioned in spaced parallel planes and parallel with the bottom of the casing, a rotatable insulat-v ing member mounted on a shaft secured to the cover and rotatable with the shaft about its axis at right angles to the planes of the terminals, connecting members mounted on each side of the insulating member and projecting therefromin the planes of its terminals to connect the terminals of each pair when the switch is closed, and prevent a movement of the insulating member, connecting members, and the shaft in a parallel direction of the axis ofthe shaft, means interlocking the cover with the shaft permitting relative rotation but not relative movement along the axis of the shaft and an interlock between the casing and cover to prevent removal of the cover while the switch is closed.

18. A switch comprising a casing and a rotatable cover removably secured together by a screw threaded connection therebetween, external means operable by a key to lock the casing and cover against rotation by unauthorized persons, insulated terminals secured to the casing, contact plugs to be connected to and disconnected fro-m the termian authorized person while the switch is closed or replacement of the cover while the switch is in a position to connect .the

and a removable cover, switch mechanism ro-Y i tatably mounted on the cover within the receptacle and removable with the cover` only and connecting terminals projecting through the walls of the receptacle to connect to cables exterior of the receptacle, the switch mechanism interlocked with thek terminals whenf closed and preventing removal of the cover,

concealed interlocking meansv between'the cover and casing and disengaged by rotation of the cover, when the switch mechanism is outy of engagement with the terminals, means to prevent rotation of the cover to remove the same-,by an unauthorized person and means on the casing coacting with the switch mechanism to prevent removal or replacement of the cover and switch mechanism by an authorized or unauthorized person until the switch mechanism stands in an open relation to theV terminals. j

Y In testimony whereof I affix kmy signature; HOMER P. CHANDLER. 

